[PATCH] D72362: [clang-tidy] misc-no-recursion: a new check

[Artem Dergachev via Phabricator via cfe-commits]

NoQ added inline comments.


================
Comment at: clang-tools-extra/test/clang-tidy/checkers/misc-no-recursion.cpp:153
+// CHECK-NOTES: :[[@LINE-7]]:3: note: Frame #1: function 'boo' calls function 'bar' here:
+// CHECK-NOTES: :[[@LINE-14]]:18: note: Frame #2: function 'bar' calls function 'boo' here:
+// CHECK-NOTES: :[[@LINE-15]]:18: note: ... which was the starting point of this call graph
----------------
lebedev.ri wrote:
> lebedev.ri wrote:
> > NoQ wrote:
> > > Aha, yeah, the warning is present, i guess that part is correct, but look how your note `function 'bar' calls function 'boo' here:` doesn't really point into the body of 'bar'. In this case it still makes sense because it's easy to see that 'foo' is called from 'bar', but the chain of default arguments may be arbitrarily long (what if 'boo' has yet another default argument?). You might want to add a separate facility just to handle this edge case.
> > To make this more readable, the diag is:
> > ```
> > /builddirs/llvm-project/build-Clang9-unknown/tools/clang/tools/extra/test/clang-tidy/checkers/Output/misc-no-recursion.cpp.tmp.cpp:138:5: warning: function 'boo' is part of call graph loop [misc-no-recursion]
> > int boo();
> >     ^
> > /builddirs/llvm-project/build-Clang9-unknown/tools/clang/tools/extra/test/clang-tidy/checkers/Output/misc-no-recursion.cpp.tmp.cpp:140:6: warning: function 'bar' is part of call graph loop [misc-no-recursion]
> > void bar() {
> >      ^
> > /builddirs/llvm-project/build-Clang9-unknown/tools/clang/tools/extra/test/clang-tidy/checkers/Output/misc-no-recursion.cpp.tmp.cpp:138:5: note: Example call graph loop, starting from function 'boo'
> > int boo();
> >     ^
> > /builddirs/llvm-project/build-Clang9-unknown/tools/clang/tools/extra/test/clang-tidy/checkers/Output/misc-no-recursion.cpp.tmp.cpp:145:3: note: Frame #1: function 'boo' calls function 'bar' here:
> >   bar();
> >   ^
> > /builddirs/llvm-project/build-Clang9-unknown/tools/clang/tools/extra/test/clang-tidy/checkers/Output/misc-no-recursion.cpp.tmp.cpp:139:18: note: Frame #2: function 'bar' calls function 'boo' here:
> > void foo(int x = boo()) {}
> >                  ^
> > ```
> > Am i looking at this wrong, or all the info is present?
> Edit: right, `bar->foo` edge is not shown there.
Yup. And, well, semantically it's kind of correct, because it's not `foo()` that calls `boo()`, but it's `bar()`'s responsiblity to call `boo()` directly before calling `foo()`. So it's more like a three-way relationship:
```
misc-no-recursion.cpp.tmp.cpp:139:18: note: Frame #1: function 'bar' calls function 'boo' here:
void foo(int x = boo()) {}
                 ^
misc-no-recursion.cpp.tmp.cpp:141:7: note: ...in order to compute default argument for function 'foo' here:
  foo();
      ^
```
So i'd imagine `CallRecord`s potentially containing arbitrarily long chains of backreferences from a default argument initializer to the respective `CXXDefaultArgExpr` that we're currently visiting (which may in turn be part of another default argument initializer, given that those are arbitrary expressions).

(it's of course up to you whether you want to deal with this immediately or later, i'm just ranting, don't mind me)


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D72362/new/

https://reviews.llvm.org/D72362